This application claims priority under 35 USC xc2xa7119 of application number BO 2000A 000678, filed on Nov. 21, 2000 in Italy.
The present invention relates to a control method for an electromagnetic actuator for the control of an engine valve.
As is known, internal combustion engines of the type disclosed in Italian Patent Application B099A000443 filed on Aug. 4, 1999 are currently being tested, in which the movement of the intake and exhaust valves is performed by electromagnetic actuators. These electromagnetic actuators have undoubted advantages since they make it possible to control each valve according to a law optimised with respect to any operating condition of the engine, whereas conventional mechanical actuators (typically camshafts) make it necessary to define a lift profile of the valves which is an acceptable compromise for all the possible operating conditions of the engine.
An electromagnetic actuator for a valve of an internal combustion engine of the type described above normally comprises at least one electromagnet adapted to displace an actuator body of ferromagnetic material mechanically connected to the stem of the respective valve. In order to apply a particular law of motion to the valve, a control unit drives the electromagnet with a current that varies over time in order appropriately to displace the actuator body.
Known control units in particular control the voltage applied to the coil of the electromagnet in order to cause a current intensity determined as a function of the desired position of the actuator to circulate in this coil. It has been observed from experimental tests, however, that known control units of the type described above are not able to guarantee a sufficiently precise control of the law of motion of the actuator body.
The object of the present invention is to provide a control method for an electromagnetic actuator for the control of an engine valve that is free from the drawbacks described above and that is in particular simple and economic to embody.
The present invention therefore relates to a control method for an electromagnetic actuator for the control of an engine valve as claimed in claim 1.